I have know idea what is going on I updated my XBMC the other day and everything worked perfectly even earlier today it worked . just now I tried to load a couple of different video and they play good but no sound and in the upper right it shows the sound crossed out. I seen that and thought that maybe I was muted but it isn't and sound works for everything but xbmc I even checked to make sure that the proper card was listened in the XBMC software , updated the audio drivers even uninstalled rebooted and re installed the xbmc software grrr I was hoping that it was a late April fools joke but it isn't.
Any one have any suggestions because I really can't think of anything else to do

that didn't work , I did totally uninstall but this time I removed my profile and then ran ccleaner to get rid of every single registry left over and rebooted installed every thing is working once again , strange I haven't had anything happen to me like this since my windows XP days lol
Not sure what the problem was but it is working now.
Thank you for the reply though :)

How do you have your system setup? Are you using the sound thru HDMI on your gpu or are you using the sound from your motherboard? Disable whichever one you are not using in "Playback Devices". This should force XBMC to use the other. You can also try fiddling with the sound source in XBMC settings. I believe its under System/Audio in XBMC.

Edit:
Noticed you got it working.
There was/is a bug in Catalyst that caused issues with HDMI audio at times requiring the cable to be unplugged and plugged back in to reset it or of course restart the machine to do so. Maybe try a new catalyst(or beta) if it happens again.